Potential AC problem...

[Beau]

Hi Guys,

So I've been having a strange clicking sound coming from the passenger side glove box area. On further inspection it seems to be coming from the Fan motor area. The clicking sound is louder than a relay clicking so I reckon it's something that needs to be sorted sooner than later... It only occurs when the AC itself is on.

Second symptom is when at idle, I get a vibration that last for a few seconds as the AC switches on/off - I assume maybe the AC compressor clutch? So I'm thinking whatever that clicking sound is also controls the clutch switch on the compressor.

Does anyone have any idea what exactly is clicking in the first place? Is there any electronic actuator inside these blower motors?

Any help appreciated,

Beau

 

[StarCruiser]

Hi Beau, I'm not sure about the 90 series but there should be a sight glass somewhere in the pipework for the AC. It will be on the thinner pipes that go back from the condenser rad at the front back to the cabin. When you've found it, Shen a torch in there and see if you see bubbles flowing past.

My guess is that it is short of gas and needs recharging as it is cycling on low pressure. The clink you hear is probably the relay and the clutch pulling in.

 

[Beau]

Hi Beau, I'm not sure about the 90 series but there should be a sight glass somewhere in the pipework for the AC. It will be on the thinner pipes that go back from the condenser rad at the front back to the cabin. When you've found it, Shen a torch in there and see if you see bubbles flowing past.

My guess is that it is short of gas and needs recharging as it is cycling on low pressure. The clink you hear is probably the relay and the clutch pulling in.

Thanks for the reply starcruiser.

Yes, I know the glass piece you're talking about. I've looked through it and see no visible bubbles and the level is about the half way mark. I've also recently tried topping up the system and it read well and pressured.

Though I do recall seeing some oil below the AC condenser a few months back so suspect a slight leek in the system.

I'm used to hearing the AC cycle, but what I'm hearing is a slightly louder click than normal that cycle on/off every 5 seconds or so. I forgot to add, at night time when the temps fall the clicking noise happens less often, compared to during the day when it's hot.

 

[StarCruiser]

You say you've tried topping up the system- how? Why?

When you say the level is at the half way mark, which sight glass are you referring to? One that is horizontalish in pipework or one in the top of the filter/drier/receiver? Perhaps post a photo? There should be no half way, it should be clear or full of bubbles rushing through. This is with the system on and running of course.

Is the car equipped with an electric or engine driven fan?

 

[Beau]

You say you've tried topping up the system- how? Why?

When you say the level is at the half way mark, which sight glass are you referring to? One that is horizontalish in pipework or one in the top of the filter/drier/receiver? Perhaps post a photo? There should be no half way, it should be clear or full of bubbles rushing through. This is with the system on and running of course.

Is the car equipped with an electric or engine driven fan?

AC wasn't blowing too cold, so topped it up with one of those DIY cans. Only used about half the can as pressure were well within spec (according to the gauge).

I've just looked through the eye piece, it's the one that comes off the top of the dryer. It's the only one in the AC system I can see. When the truck is running, it's full of liquid with no bubbles.

I've checked pressures today with a manifold gauge set, and got around 30-40 PSI on the low side, and between 250-300 on the high side at a ambient temp of around 25c. Do these values sound right?

I'm inclined to empty the system and recharge with fresh fluids, but I can't find the spec of how much volume refrigerant these trucks take, any idea? It's the better way I've read of adding refrigerant compared to pressure.

 

[Dave]

You've over filled it, so now its tripping out on high pressure. You cant fill by the crappy gauge on a can. You need to find and fix the leak, then vacuum, then charge by weight.

 

[StarCruiser]

Beat me to it Dave. Exactly the problem.
Exactly what's needed.

 

[Beau]

Thanks for the advice guys, I came across the exact same thought thinking back at it. Never trusting pressure readings again as a suitable way of filling up the system...

So this is what I did. Bought a manifold AC set, Vacuum pump, and some proper R134a Refrigerant and set to work.

Extracted all of the old refrigerant properly and then vacuumed the system. Held vacuum which indicated no leaks. Vacuumed again for couple hours, and then added 700 grams of fresh R134a back into the system.

AC works well, and no more random clicking occurring!

Whats even better, is I learnt a lot about AC through this, was well worth it!

 

[StarCruiser]

That sounds excellent Beau.

Just one point though, holding vacuum does not guarantee no leaks I'm afraid. Vacuum is a maximum of 14.7 psi FROM OUTSIDE, which is firstly nowhere near system pressure and secondly is working to suck seals in and leaks closed, rather than push them away. Thirdly, what did you measure it with? Fridge gauges are not accurate enough on vacuum, fridge engineers use a Torr gauge, which reads lower pressures more accurately. Also, did you purge your gauge lines with refrigerant or vac them out before finally connecting to the refrigerant?

Now, what you have done is all correct and, I must say, very impressive, but vacuum as a leak check is only one of several methods and is a very course one for the above reasons. To properly leak check the system needs pressurising with nitrogen and an accurate gauge connecting to see if it drops over a set time. Thirdly a leak checker over every joint will give the finest check while the system is running.

As a caution here, you must be very careful with refrigerant. If you get liquid spray out of a connection (a gauge line being disconnected for example) avoid getting it in your eyes as it can freeze the eyeball instantly…not nice.

Finally, did you add any PAG oil? My system was completely empty of it, blew it out with nitrogen, not a drop left and it had never been opened. Now you may not have needed it, but it certainly won't contain what it was originally charged with.

Over all, well done Beau, I don't suppose there's many of us on here that have recharged our own AC.

 

[Beau]

Starcruiser,

Thanks for the heads up. On top of checking for leaks via Vacuum, I also used an electronic freon/hallogen detector on all joints and pipe work and thankfully I got no signs of leaks.

I did use a fridge gauge, was the only option I had really. And yes, before entering new refrigerant I purged the line to not draw back any air into the system. If I wasn't in a rush, I would have bought some UV AC dye for the system as well.

The PAG oil, I was a little concerned about. I chose to only add 80 grams of PAG46. This was a little bit of guesswork as most of the threads I read said not a lot of oil comes out the system, but I guess this varies. Is there any official way of checking if there's enough oil in the system?

 

[StarCruiser]

The only way to know how much oil there is in the system is to start from empty. Too much and you can hydraulic lock the compressor but I believe it would need to be way over. It is a constant problem fridge engineers face and it does leak out as a vapour (I know, I didn't believe it when I heard it either) which is the only way mine could have lost it.

 

[Beau]

Yeah, I felt having too little might be better than too much. Would the compressor run any different on low oil. Would it get hot? Any idea on how much is too much. Lets say the system takes 500 grams of PAG. And so it already has about 400, and you put an additional 500 thinking it's empty. It now has 900 grams, nearly twice the amount, would this be enough to kill it?

Obviously the only way from starting from scratch is to drain the oil from the actual compressor. Not that I'm going to do that, but just out of interest does this require removing the compressor, or can it actually be done on the engine?

 

[StarCruiser]

There is no way of knowing, unless the compressor seizes up. The oil doesn't stay in the compressor but gets carried around the system with the refrigerant. There are different types of compressor also, mine is a multi piston but there are scroll compressors about, don't know which yours is. Heat or cold won't indicate oil content as the compressor will get hot by doing its job on the discharge side and cold on the inlet side.

Judging by mine, simply having some oil in the system should mean the compressor is ok. If you wanted to check the amount of oil, and your compressor is the same type as mine (multi piston) then have a look at the Frankenstein thread on compressor rebuild. With the rest of the system empty, and the compressor rotated several times, all the oil in a new compressor appear in the discharge area in a sort of hopper up to within 1/4" or so of the top. Returning to that level and blasting anything else out of the system would be the only way to get an accurate fill of oil.
They can take an overfill but I have no idea how much is too much.

And of course, now you've got it sorted the weather has turned to poo!! I'm blaming you!

 

[Beau]

Good to know! All this has been a new learning curve really, never dealt with AC before but it's nice to know how it all works now.

Here in Florida, we're having highs of 30 Celsius on the daily, AC is very much needed!

 

[StarCruiser]

You can go off some people!!!

Thought you were down as being in Milton Keynes anyway…?

 

[Beau]

You can go off some people!!!

Thought you were down as being in Milton Keynes anyway…?

haha

Should probably change that. Been in Florida for the past year and half now. Cruisers been here coming up a year in September. How time flies!